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Schottky barrier heights of Transition Metal Dichalcogenides and other layered systems

Speaker: 
John Robertson (Cambridge University, UK)
Date: 
Wed, 01/04/2015 - 11:00am to 12:00pm
Location: 
Physics Conference Room (S13-M01-11)
Host: 
CA2DM
Event Type: 
Seminars

Abstract

The Schottky barrier heights of the layered transition metal dichalcogenides (TMDs) have been calculated using density functional theory. The calculated Schottky Barrier heights are found to depend quite weakly on the metal work function, with a pinning factor of S~0.3.  This indicates that TMD Schottky barriers follow the metal induced gap state (MIGS) model, like three-dimensional semiconductors, despite the two-dimensional bonding of TMD layers. This is because the bonding between the contact metal atoms and the TMD chalcogen atoms is covalent/ionic, and not of a van der Waals type. The metal Fermi level is pinned in the upper gap in MoS2, but pinned near midgap in most other TMDs. Thus, ambipolar contacts can be achieved by avoiding MoS2, or by using a high work function electrodes like MoO3 on MoS2. Contacts for black phosphorus are also covered.

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